During integrated circuit fabrication, various films are needed on the active circuit region of the wafer, i.e., the main interior region on the front side, but are undesirable elsewhere. Deposition processes, including chemical vapor deposition (CVD) and physical vapor deposition (PVD) processes, often deposit films out to the edge of the front side of the silicon substrate or wafer, generally beyond the printed or active area. In many cases, deposition of the films beyond the active circuit region creates difficulties in process integration. For example, drying and baking photoresist leaves a thick berm of material at the edge of the wafer, which can peel and flake during subsequent processing or handling. Other films susceptible to problematic delamination include tungsten, copper seed and organosilicate glass (OSG) films.
Methods of preventing deposition on unwanted areas or removing unwanted films have included using edge exclusion hardware (e.g., a shadow ring) and wet chemical etches using an acid spray directed at the edge. However, edge exclusion hardware may not be compatible with certain deposition systems, e.g. certain plasma deposition systems, and even in compatible systems, may cause problems with deposition uniformity. Wet etching may not be desirable in certain applications as it involves handling of wet solvents. Further, films such as silicon carbide and organosilicon glass (OSG) do not etch appreciably in known wet solvents.
Accordingly, it would be desirable to be able to have new methods of selectively removing unwanted film from the edge of substrates and/or selectively forming films on the active circuit regions of a substrates.